Abrasion defleshing partially tanned fur-skins



United States Patent Britain No Drawing. Filed Jan. 30, 1963, Ser. No. 255,066 Claims priority, application Great Britain, Mar. 29, 1960, 11,091/ 60 13 Claims. (Cl. 894.14)

This application is a continuation-in-part of application Ser. No. 98,005, filed March 24, 1961.

This invention relates to the dressing or tanning of furskins.

Certain fur-skins such as Canadian squirrel have a nuturally tight grain that is the fibre bundles of the skin texture are closely knit together. The fibre structure of the pelt is close-knit and it is normally difficult to dress such fur-skins by normal methods. In the leather industry, it is not essential to preserve the hair or wool firmly fixed to the pelt. Indeed the process of liming not only removes hair or wool, but also assists in breaking up the fibre bundles of the leather. A bate which is a form of enzyme is also employed to dissolve out the interfibrillary substance. Leather which has been limed and bated has a relatively open fibre structure and it is very easy for tanning materials to penetrate. Such processes cannot be used in dressing fur-skins since the bate and lime attack the hair which cannot be tolerated.

In the conventional methods of dressing or tanning furskins the raw skins are first soaked in water or salt water to soften them and put them into condition for what is known as fleshing that is the removal of the thin membrane of the flesh on the pelt side of the skin, which membrane is known as the areolar tissue and is impermeable to water and the liquid tanning or dressing materials. The act of fleshing is to remove the areolar tissue leaving the corium free to absorb the dressing or tanning materials, it being of essence in dressing or tanning that the whole of the skin from the pelt side to the fur side is completely permeated by the pickle or tan in order that the skin can become a permanent product.

Fleshing is a highly skilled operation, particularly with the smaller and more valuable furs, and is carried out normally by hand on a fleshing bench, the skin being skilfully drawn across a large fixed razor-sharp knife. An alternative method, also highly skilled is to employ a circular rotating blade across which the skins are deftly drawn to remove the areolar tissue. The flashing greatly increases the cost of dressing or tanning fur-skins to permanent products acceptable to the trade, particularly for making up into garments.

The known methods of dressing or tanning fur-skins, therefore, start with soaking and preparing for fleshing, then fleshing and, after fleshing, applying the acid pickles or mineral tannages followed by fixation of oil to give a soft permanent product acceptable to the user.

Normally the dressing or tanning is effected by immersing the fleshed skin in a bath containing the acid pickle or tan for suflicient time to ensure that the ultimate product will be permanent, a suitable pickle being composed of various acids such as sulphuric acid, formic acid, acetic acid, lactic acid, etc. to which is added sodium chloride as common salt to prevent the skin swelling due to the effect of the acid thereon. Suitable mineral tans include alum, aluminium sulphate, chrome tan, etc.

Although the initial pickle or tan can be applied by immersion, it can also be applied by hand as a poultice on the pelt side of the fur-skin. The process known as hot room leathering is usually employed on thin pelted skins, mainly long haired fur-skins such as foxes, the hair of "ice which would become heavily matted in a kicking operation as hereinafter described, and other thin pelted skins such as rabbit skins and lamb skins. With such thin pelted skins there is sufficient penetration of the pelt by the pickle or tan by poulticing and the poulticed skins, after oiling, are normally hung up in a hot room (-100" F.) for suflicient time to fix the oils in the skin, 12 to 36 hours being the usual drying period.

It is important to note that the skin treated in a pickle or tan bath, although forming a permanent product, would dry hard and horny and to render it acceptable to the trade it is essential to apply oil to the skin to render it capable of maintaining its soft condition by acting as a lubricant between the fibres of the skin protein structure so that the fibres are prevented from sticking together in bundles. Normally the oils employed are animal, fish and mineral oils, or a mixture of them, some of which can be unsaturated oils. These oils have to be forced as by pounding into the skin and what is known as a kicking machine can be employed which heavily pounds the skins impregnated with the oil until fixation of the oil by oxidation and some penetration of the oil into the skin has taken place. Kicking however is not normally employed with the aforesaid thin pelted skins.

This process results in the hair on the fur side of the skin becoming sticky and the surplus oil has to be removed and, in some cases, the skins are then bleached and/or dyed to render them attractive in colour or appearance, but such bleaching and/or dyeing, being a steeping process, frequently results in further oiling and even redressing being necessary.

All the aforesaid processes, however, fundamentally rely on the initial step of ileshing which is by far the most expensive single step in the dressing or tanning operation since only highly skilled workmen can be employed and many difficulties may have to be overcome. Some skins such as Russian Musquash and North American Skunks are fleshed after some initial pickling or tanning has occurred, but this is a complicated process and limits the quality of the product being adopted in order to overcome the brittleness of the untanned skin.

It is the main object of the present invention to provide an improved method of dressing or tanning raw fur-skins Without any necessity of the fieshing operation as such.

According to the present invention a method is provided of tanning or dressing raw fur-skins having areolar tissue attached to the flesh side to enable said tissue to be removed by abrasion and to effect partial tanning of the skin, which method comprises immersing said fur-skin in a mixture of a tanning liquor and a penetrant consisting essentially of an emulsified sulphited unsaturated natural oil for a period of time sufficient to cure and facilitate the removal of said areolar tissue, and removing said tissue by mechanical abrasion.

Prior to the sulphited oil treatment the skin may be treated with a suitable bate and/or drawn over a rough rope to break up the solidified fat particularly in the areolar tissue. The skin may also be soaked in water or brushed with water, the water being removed in known manner or by tumbling in moist sawdust.

Preferably the aerolar tissue is removed as a partly cured lamina by a simple buffing operation but other means may be employed which do not harm the skin and give a satisfactory nap, such for example as a staking machine which employs a rotating head on which are fixed a number of blunt blades fixed at different angles such as are used in woodworking.

The sulphited natural unsaturated oil may be any such oil, for example sulphited cod oil, sulphited sperm oil or sulphited marine animal oil, the sperm oil being preferred. The acid tanning liquor may be for example made up of a solution containing 50 gr. common salt and 2 cc. formic acid per litre, and the mineral tanning liquor may be for example 40 gr. common salt and 40 gr. alum per litre.

In a preferred method the unfleshed skirt is treated with a sulphited natural unsaturated oil mixed with the mineral tan or acid pickle, particularly to dress the skin and effect at least a partial dress of the areolar tissue. After the areolar tissue has been removed as by a buffing operation, the skin is re-immersed in a mixture of sulphited oil and mineral tan or acid pickle for a further period to ensure complete penetration of the fur-skin, thereby completing the dressing or tanning process. The usual drying and cleaning is then carried out in the manner well known in the art, including tumbling the fur-skins in dry sawdust to remove dirt and oil.

In the preparation of the fur-skin prior to the combined treatment with sulphited oil and mineral tan or pickle, a mild alkaline treatment is sometimes applied to the fur-skin after the initial soaking stage with the water or salt water, thus helping to soften the areolar tissue and to facilitate its penetration and the penetration of the furskin by the said materials.

While the above processes are adequate for treating light fur-skins, such as mink, further treatment may be necessary with very tough fur-skins, such as American Opossum or Musquash and for such purposes the oiling is reinforced by the addition of a hand oiling stage later in the process or by any other known oil process, such as kicking, well known to one skilled in the art.

Tight grained fur-skins such as Canadian Squirrels or American Muskrats become even tighter if immersed in alum tanning solutions plus emulsified sulphited unsaturated natural oil and for such skins it is preferred to use an acid pickle plus sulphited oil as a preliminary step of the invention to treating the skin with the emulsified oil and tan to the areolar tissue sufficiently to permit it to be removed by mechanical action. A suitable acid pickle consists of common salt (which is present to control swelling) plus mineral or organic acid or mixture of such acids, together with a small quantity of an ammonium salt which helps to maintain a stretchy pelt. The invention is not restricted to a particular acid pickle, and indeed, a large number of such pickles in common use by fur-skin dressers and almost any acid pickle conventionally used in the fur dressing trade would be suitable,

in conjunction with the sulphited oil. The following are examples of suitable oils:

Example 1 salt formic acid ammonium chloride sulphited oil Example 2 salt sulphuric acid lactic acid ammonium sulphate sulphited oil gr. cc.

1 litre.

1 litre.

Example 3 salt alum

ammonium chloride 1 litre. formic acid sulphited oil 50 gr. gr. 5 gr. 2 cc. cc.

Example 4 40 gr. salt 40 gr. alum 1 gr. soda ash 30 cc. sulphited oil 1 litre.

In order that the invention may be more clearly understood Example 5 which is an example of the treatment of a light fur-skin, such as a mink skin, will now be described.

Example 5 he fur-skin removed from the animal is first soaked and treated in the conventional manner to remove any surface fat, if any, but this step forms no part of the present invention and requires no further description here. The fur-skin is then immersed for one hour at 30 C. in a bath containing, per litre, 30 grams of common salt and /2 gram of soda ash. The temperature is not critical and it has been found that the process is successful anywhere in a temperature range of 2040 C.; the temperature must be below about 120 F. at which the fur-skin undergoes a change to gelatine, and the temperature must be above that at which freezing occurs. This immersion is preferably carried out overnight.

The skin is then removed from the bath and hydroextracted and thereafter immersed in a bath at C. containing, per litre, grams of common salt, 40 grams of alum, 1 gram of soda ash and 30 cc. of sulphited oil, the temperature again not being critical as aforesaid and success having been achieved with baths at temperatures in the range 2040 C. This further immersion is carried out over about 16 hours but it may be for longer or shorter periods, although it has been found that for longer periods the quality of the final product is not improved but for shorter periods the product tends to be less satisfactory below twelve hours immersion and after only three hours immersion the product is quite unsatisfactory.

After this prolonged immersion the fur-skin is removed from the bath and hydro-extracted and thereafter tumbled in sawdust to put the pelt in condition for the buffing operation.

The fur-skin is then buffed using a rotating roller covered with a suitable abrasive material such as an SS-grain sanding paper and by this operation the areolar tissue is very easily removed. Buffing can be carried out in any conventional manner as by using a small vertical cylindrical bobbin preferably rotating in a vertical plane, and covered with an SS-grain sanding paper. It is also possible to use a wheel which resembles a motor car wheel and which is rotated in a horizontal plane in the same way as a car wheel. This wheel has its surface spread with glue and carborundum powder, of a suitable mesh, is sprinkled on the glued surface. Preferably for the initial stage of the bui'hng operation a wheel having a 30 to 40 size grain glued thereon has been found to be suitable and thereafter it was found convenient to buff further with a wheel having a grain size of to glued thereto so as to obtain a smoother nap on the surface of the skin. The grain size and density is not critical but too much grain has too rapid an action and too little grain will slow up the process. When the glue has set, the Wheel is ready for use, and whilst rotating the wheel the skin is pressed against the moving abrasive surface. This process is known as Wheeling in the leather trade, and is used for processing gloving, clothing and suede leathers such as kid or calf.

However any other manner of removing the at least partly cured areolar tissue, other than by fieshing may be employed, for example, on a staking machine.

After the buffing or any other method of removing the areolar tissue the skin is then re-immersed in a bath which may be the same or similar sulphited oil bath or conventional acid, acid mineral tan, tan or pickle and left for a further period such as 16 hours as herein defined, thereafter being hydro-extracted and re-drummed in sawdust in the convention manner. The bath solution will be selected in the conventional manner according to whether a thin or plump dressing is required as will be well known to one skilled in the art and requires no further description. In general, mineral tans tend to give a stouter leather, but the higher the pH. the thinner the leather is likely to be. Example 4 will give a thicker leather than Example 1 or 2. The period of re-immersion may be as short as 4 hours at 30 C. or overnight, whichever is more convenient. Certain thin pelted skins such as Persian lamb, mink or musquash need not, however, necessarily be re-immersed providing, as frequently occurs, the pelt of the skin beneath the areolar tissue has been fully tanned or dressing in the initial process.

If desired hand oiling or drum stutfing, e.g. kicking. may be inserted at this stage for the tougher skins such as American opossum or musquash. Finally the furskin is finished and shaped in the usual way.

Hitherto Persian lamb skin has not usually been fleshed as other skins such as mink or musquash, but can be and normally is fleshed by a much lighter hand process not involving the skilled fleshers and can even be carried out by women fleshers, but the Persian lamb skins can be treated by the process according to the invention so that even the simpler fieshing step can be eliminated.

While the preferred method is to dip the unfieshed skin in the soaking bath and later in the pickling or tanning bath with the sulphited oil, it is possible to treat only the pelt surface of the skin in the initial stage by poulticing the pelt surface first with the soaking water or salt water and thereafter with the pickle or tannage with the impregnant and continuing this process until the areolar tissue of the fur-skin is rendered sufficiently cured for it to be removed as by the bufling operation.

In yet another method this skin can be passed between a series of nips formed by light pressure rolls, the lower roller of each pair forming the nip dipping in a bath, first of the water or salt water to soak the flesh and thereafter in the pickle or tan bath. The upper roller of each pair applies sutficient pressure to the fur-skin to ensure contact of the flesh membrane with the impregnating roller.

It will be found that by the method according to the present invention a highly satisfactory dressing or tanning of fur-skins of all kinds is achieved and the fleshing step is eliminated, thereby very greatly reducing the cost of the tanning process as well as speeding it up.

Some skins, such as beaver, are conventionally unhaired before the fieshing operation and the present invention may be used for removing the areolar tissue of such skins, in which case the skins after unhairing are subsequently treated as herein set forth, including butfing or like treatment, to remove the cured areolar tissue.

I claim:

1. Method of dressing raw fur-skins having areolar tissue attached to the flesh side to enable said tissue to be removed by abrasion and to effect partial tanning of the skin, which comprises immersing said fur-skin in a mixture of a tanning liquor and a penetrant consisting essentially of an emulsified sulphited unsaturated natural oil for a period of time sulficient to cure and facilitate the removal of said areolar tissue, and removing said tissue by mechanical abrasion.

2. Method of dressing raw fur-skins having areolar tissue attached to the flesh side to enable said tissue to be removed by abrasion and to effect tanning of the skin, which comprises immersing said fur-skin in a mixture of a tanning liquor and a penetrant consisting essentially of an emulsified sulphited unsaturated natural oil for a period of time sufficient to cure and facilitate the removal of said areolar tissue, removing said tissue by mechanical abrasion, and then immersing the skin again in said mixture to complete the dressing.

3. The method of claim 1 in which the immersion is carried out maintaining the temperature of the mixture 'between about 20 and 40 C.

4. The method of claim 1 in which the sulphited unsaturated natural oil is a sulphited marine animal oil.

5. The method of claim 1 in which the treating mixture is applied only to the pelt surface of the skin.

6. The method of claim 1 in which the tanning liquor is a mineral tan.

7. The method of claim 1 in which the tanning liquor is an acid pickle.

8. The method of claim 1 in which the immersion period is from about 12 to 24 hours.

9. The method of claim 2 in which the second immersion is followed by oiling of the skin.

10. The method claim 2 in which the fur-skin is pretreated with an aqueous salt solution prior to immersion.

11. The method of claim 2 in which the fur-skin is pretreated with an aqueous salt solution and then with a dilute solution of an alkali prior to the immersion step.

12. A method of dressing raw fur-skins having areolar tissue attached to the flesh side to be removed by abrasion and to etiect tanning of the skin comprising steps whereby the fur-skin removed from the animal is treated to remove any surface fat, immersed for about one hour at a temperature of below F. in a bath containing, per litre, 30 gms. of common salt and /2 gm. of soda ash, removed from the bath and treated to remove substantially all the liquid therefrom, immersed for at least 12 hours in a bath at less than 120 F. and containing, per litre, 40 gms. of common salt, 40 gms. alum, 1 gm. soda ash and 30 cc. sulphited oil, removed from the bath, treated to extract substantially all the bath liquid therefrom, treated in sawdust to prepare for the removal of the areolar tissue, removing the areolar tissue mechanica lly other than by fleshing, reimmersed for at least 12 hours in the said sulphited oil bath, removed from the bath, treated to remove substantially all the bath liquid, treated with sawdust to clean the fur-skin, and finally finished and shaped.

13. The method of claim 4 in which the sulphited marine animal oil is sulphited sperm oil.

References Cited by the Examiner UNITED STATES PATENTS 85,030 12/68 Schrnitz 5l28l 2,700,590 1/55 Biery et al. 8-94.12 2,807,557 9/57 Carney 8-94.14

OTHER REFERENCES Austin, Fur Dressing and For Dyeing, pages 38-49, 58-63, pub. 1922 by D. Van Nostrand Co., N.Y.C.

Proctor, The Principles of Leather Manufacture, 2nd ed., pages 457-474, pub. 1922 by D. Van Nostrand C0, N.Y.C.; pages 461-465 are especially pertinent.

Ciba Review, Ocober 1952, pages 3384-3388.

NORMAN G. TORCHIN, Primary Examiner. 

1. METHOD OF DRESSING RAW FUR-SKINS HAVING AREOLAR TISSUE ATTACHED TO THE FLESH SIDE TO ENABLE SAID TISSUE TO BE REMOVED BY ABRASION AND TO EFFECT PARTIAL TANNING OF THE SKIN, WHICH COMPRISES IMMERSING SAID FUR-SKIN IN A MIXTURE OF A TANNING LIQUOR AND A PENETRANT CONSISTING ESSENTAILLY OF AN EMULSIFIED SULPHITED UNSATURATED NATURAL OIL FOR A PERIOD OF TIME SUFFICIENT TO CURE AND FACILITATE THE REMOVAL OF SAID AREOLAR TISSUE, AND REMOVING SAID TISSUE BY MECHANICAL ABRASION. 